Polyvinyl chloride (PVC) is a versatile polymer which is used in many applications such as water piping, floor tile, exterior vinyl siding, electrical wire insulation, shower curtains and synthetic leather. Plasticizers are added to PVC to improve flow, and therefore processability, as well as to reduce the brittleness of the product. A plasticizer is a material incorporated in a plastic to increase its workability and its flexibility or distensibility (i.e., elongation). This is achieved by lowering the glass transition temperature (“Tg”), thereby producing a change in properties from those of a hard, brittle, glasslike solid to those of a soft, flexible, tough material. The vast majority of plasticizers used today are monomeric ester-types. Phthalates such as diisononyl phthalate, diisodecyl phthalate and di(2-ethylhexyl) phthalate (dioctyl phthalate, DOP) are well known and commonly used plasticizers. Further, plasticizers are usually added to PVC on hot rolls or in a hot mixer such as a Banbury. The plasticizer content varies widely depending on the end use of the material; however, typically plasticizer content will be approximately 5 to approximately 50% by weight.
When evaluating which plasticizers should be used for a particular application, the permanence of the plasticizer, in addition to miscibility with the PVC, is crucial. Permanence refers to the stability of plasticizer within the blend. More specifically, plasticizers, especially those with low molecular weights, tend to be migratory in that they tend to move to the surface of the blend where they subsequently evaporate and/or may be removed by soapy water, solvents, oils, etc. These problems are minimized by using high molecular weight polymers. Unfortunately, very high molecular weight polymers may present processing and compatibility problems, cause poor low temperature flexibility, and become costly.
Copolymers of ethylene, carbon monoxide and a termonomer(s), such as vinyl acetate, have been used as plasticizers in blends with PVC to produce flexible films, as well as, rigid and semi-rigid materials. These plasticizers are compatible with PVC, lower the Tg and possess adequate permanence. However, while these plasticizers have proved to be effective, they are prepared using pure feeds of the individual monomers which can be costly. Hence, there is still a need to investigate other PVC plasticizers which are compatible with PVC and sufficiently lower the PVC resin's Tg. Additionally, less expensive avenues to produce known plasticizers should also be pursued.